What is a thymine dimer?

A thymine dimer is a type of DNA damage that occurs when two adjacent thymine bases in a DNA molecule form covalent bonds with each other, instead of bonding with their complementary adenine bases. This damages the DNA structure and can lead to genetic mutations or cell death if left unrepaired. Thymine dimers can be caused by UV radiation from the sun or other sources, chemical exposure, or other factors. Repair mechanisms within the body can often correct thymine dimers, but if they persist, they can increase the risk of skin cancer and other health problems.